2. Percent Composition Percent Composition – the percentage by mass of each element in a compound Percent = _______ Part Whole x 100% Percent composition of a compound or = molecule Mass of element in 1 mol ____________________ Mass of compound 1 mol x 100%

3.  Step 1 : Calculate molar mass  Step 2 : Divide the subtotal for each element’s mass by the molar mass.  Step 3: Multiply by 100 to convert to a percentage.

4. Percent Composition Example: What is the percent composition of Potassium Permanganate (KMnO 4 )? Molar Mass of KMnO 4 K = 1(39.1) = 39.1 Mn = 1(54.9) = 54.9 O = 4(16.0) = 64.0 MM = 158 g

5. Percent Composition Example: What is the percent composition of Potassium Permanganate (KMnO 4 )? = 158 g % K Molar Mass of KMnO 4 39.1 g K 158 g x 100 =24.7 % % Mn 54.9 g Mn 158 g x 100 = 34.8 % % O 64.0 g O 158 g x 100 =40.5 % K = 1(39.10) = 39.1 Mn = 1(54.94) = 54.9 O = 4(16.00) = 64.0 MM = 158

6. Percent Composition Determine the percentage composition of sodium carbonate (Na 2 CO 3 )? Molar MassPercent Composition % Na = 46.0 g 106 g x 100% =43.4 % % C = 12.0 g 106 g x 100% =11.3 % % O = 48.0 g 106 g x 100% =45.3 % Na = 2(23.00) = 46.0 C = 1(12.01) = 12.0 O = 3(16.00) = 48.0 MM= 106 g

7. What is the % composition of C 6 H 12 O 6 ? 7 Carbon = 72.066 g C 6(12.011 ) Hydrogen = 12.0948 g H 12(1.0079g ) Oxygen = 95.994g O 6(15.999g ) 180.155 72.066 180.155 12.0948 180.155 95.994 180.155 x100%=40.0% C x100%=6.7% H x100%=53.3% O % composition is 40.0% C, 6.7% H, and 53.3% O

8. Morphine, derived from opium plants, has the potential for use and abuse. It’s formula is C 17 H 19 NO 3. What percent, by mass, is the carbon in this compound? a)12.0 % b)54.8 % c)67.9 % d)71.6 % 8

9. Consider separate 100.0 gram samples of each of the following: H 2 O, N 2 O, C 3 H 6 O 2, CO 2  Rank them from highest to lowest percent oxygen by mass. H 2 O, CO 2, C 3 H 6 O 2, N 2 O 16/18 32/44 32/74 16/44 0.89 0.73 0.43 0.36 9 18g/mol 44g/mol 74g/mol 44g/mol

10. PERCENT COMPOSITION The percent composition can also be calculated from experimental data. A student prepares a compound of tungsten chloride from 3.946 g of tungsten and 3.806 g of chlorine. Assuming the reaction goes to completion, calculate the percent composition. %W = (mass W / mass W x Cl y )100 = (3.946 g / 7.752 g)100 = 50.9% %Cl = (Cl / W x Cl y )100 = (3.806g / 7.752 g)100 = 49.1%

11. ______1. A 5.016 g sample of chromium, Cr, combined with oxygen to give 7.333 g of an oxide compound. The percent composition of this compound is: a) 59.1% Cr, 40.9% O b) 24.4% Cr, 75.6% O c) 68.4% Cr, 31.6% O d) 71.5% Cr, 28.5% O 2. Calculate the percent composition. K 2 CrO 4 K =_____ Cr =_____ O = _____ K 2 Cr 2 O 7 K =_____ Cr =_____ O = _____